Hidden beneath the surface of New Zealand is a treasure trove of ancient marine relics that palaeontologists are keen for more Kiwis to discover.

Today a Kiwi palaeontologist is taking a group of 100 on a fossil hunt expedition in the Hurupi Stream in the Southern Wairarapa to mark International Fossil Day.

It is the first time the day has been marked in New Zealand, but Victoria University palaeontologist James Crampton hoped it would soon be celebrated regularly.

"It would be great to have local museums organising events around this date, or universities, or local rock clubs...it's just an excuse to get excited about fossils."

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He said the Hurupi stream was a great place for a fossil hunting exhibition, as it was easy to access and it was home to some great fossils.

"The stream is also always actively eroding so there is always new material being uncovered naturally," he said. "Having huge numbers of people going through is not going to cost irreparable damage."

Crampton said the stream bed often gave way to a lot of fossil shellfish that date back 10 to 12 million years, some ancient corals and old whale bones.

" A couple of years ago we found a lower jaw of a baleen whale."."

He said 10 to 12 million years ago a large part of the North Island was underwater.

"The whales would have been splashing around an island in the middle of what is now the Wairarapa.The fossils we find is the marine life living around that island."

Crawford, who got his PhD from Cambridge, in the United Kingdom, was hard-pressed to say what was his most "exciting" fossil find was.

But he recalled one particularly interesting find in Marlborough a few years ago - an ichthyosaur, a large marine reptile similar to dolphins and whales.

Crawford said there were many fantastic stories "sitting on this isolated island in the middle of the south west pacific".

"New Zealand has this amazing unique flora and fauna and an amazing fossil record that tells the story of that. It's the whakapapa of all animals and plants that live today."

Auckland geologist Bruce Hayward had recently released a book about the fossils of northern New Zealand, titled "Out of the ocean and into the fire" that details more of the land's fossil heritage.

Hayward said there have been a number of "rare and precious finds" in Auckland.

These included fossil shellfish that date back to the Jurassic age, 200 million years ago, from Tawharanui Peninsula, leaves and fern found in lake mudstone that tell the stories of the ancient forests, and evidence of sea life from 20 million years ago that hint at a warmer, subtropical climate.

Among the youngest fossils found in Auckland were caches of moa bones dug up in a swamp near Clevedon in the early 19th century and another in a Greenlane lava cave in 1957.

Crampton said celebrating the discovery of such fossils and their stories was a great way to engage people in science.

"People have a natural interest in fossils and once you get them interested in this you can get them talking about all sorts of other things, climate change, continental drift, all sorts of things."